Camelia Pasandaran – Collecting taxes is a bit more challenging this year in the wake of the Gayus Tambunan tax mafia scandal, the finance minister said on Friday.

"Rehabilitating the image of the Directorate General of Taxation has become a heavy burden after several tax-related cases," Finance Minister Agus Martowardojo said at the directorate's office. "However, we are trying hard to improve the taxation directorate general to be a credible institution."

Agus said the Finance Ministry, following the presidential decree issued this year on tax embezzlement, had established an investigative team drawn from several institutions, including the Corruption Eradication Commission (KPK), to probe the functionality of the tax office. "This is to solve the [tax mafia] cases and to uphold the law effectively," he said.

Agus was speaking during an event that saw President Susilo Bambang Yudhoyono, Vice President Boediono and other prominent politicians submit their annual tax declarations (SPT).

The tax office expects to collect more than Rp 708 trillion ($80.7 billion) this year, which Agus says is an ambitious task that will require the support of the entire nation to fulfill. Last year, the government missed its tax revenue target of Rp 661.4 trillion by 2 percent, collecting Rp 649.04 trillion.

Still, the numbers were a sign of improvement in the tax office. In 2007, less than 40 percent of registered taxpayers paid the government its due. In 2008, the number climbed to 52.8 percent, and in 2009 it improved again to 58.16 percent.

However, Agus said he feared that with so many tax corruption cases making headlines, the recent increases in tax revenue could begin to reverse as people lose faith in the system.

Last year was marked by one of the biggest graft cases in the country's history with the arrest of Gayus Tambunan, a low-level tax officer found to have Rp 28 billion stashed in bank accounts. Gayus was convicted of bribery in January, and he is expected to stand trial again for taking bribes from corporate taxpayers who allegedly used his services to ease their tax burdens.

"It has pushed the government to fix the system," Agus said. He added that the taxation directorate general was carrying out a program to address internal problems revolving around every aspect of its duties.

Bambang Soesatyo, a lawmaker from the Golkar Party, said on Thursday that based on the analysis of several experts, he estimated the tax mafia stole as much as Rp 400 trillion each year.

Last month, Yudhoyono's Democratic Party and five other parties successfully blocked a Golkar-led proposal for the House of Representatives to launch a special inquiry into corruption in the tax office. Democrats opposed the inquiry on the grounds the House would ineffective in attempting to solve the issue.

Bambang criticized the blockade on Thursday. "The proposal to use the House inquiry on tax mafia cases was indeed to investigate and fight the tax mafia," he said, adding that he believed the inquiry would have been successful in rooting out tax embezzlers.

[Additional reporting by Antara.]